1. Field
The present disclosure relates generally to the fabrication of field plate dielectrics for high-voltage semiconductors, and, more specifically, the present disclosure relates to the fabrication of tapered field plate dielectric for high-voltage semiconductor devices.
2. Description of Related Art
Electronic devices use power to operate. Power is generally delivered through a wall socket as high voltage alternating current (ac). A device, typically referred to as a power converter or as a power supply, can be utilized to transform the high voltage ac input into a well regulated direct current (dc) output through an energy transfer element. One type of power converter is a switch mode power converter which is commonly used due to its high efficiency, small size, and low weight to power many of today's electronics. Many switch mode power converters that provide electricity to electronics such as tablet computers, smart phones, and LED lights rely on power semiconductor devices that can handle high-voltages. For example, semiconductor devices in cell phone chargers may be required to handle peak voltages of up to 600 V without breaking down. Some of these high-voltage devices handle high voltages by spreading electric fields over larger areas of semiconductor, which prevents electric fields from exceeding breakdown thresholds. To aid in the spreading of the electrical fields, sometimes field plates are used.
One type of high voltage transistor is a vertical thin silicon (VTS) high voltage field effect transistor (HVFET). For example, FIG. 1 depicts an example VTS HVFET 10 built on wafer 11. VTS HVFET 10 includes source regions 15a and 15b, body region 14, and drain regions 12 and 13 (which include a long drain extension) in a silicon pillar. A potential applied to gates 17a and 17b may modulate a channel in body region 14 and control conduction between source regions 15a and 15b and drain regions 12 and 13. The potential of body region 14 may be controlled by body contact 16. HVFET 10 also has field plate 18 separated from the silicon pillar by field plate dielectric 19. Field plate 18 allows for an increase in breakdown voltage by spreading high voltage drops over larger areas in the extended drain region (i.e., spreading out electric fields).